“If you want to lose weight, you have to exercise ‘intensely’?”… Why does it actually make you gain more weight?

A study published in Medicine & Science in Sports & exercise found that high-intensity exercise reduced overall activity and heat production, even without changes in food intake.

Researchers at the University of Tsukuba in Japan divided mice into three groups: high-intensity exercise, moderate-intensity exercise, and rest. They monitored the mice's physical activity and core body temperature, indicators of heat production, before and after exercise.

The study results showed that, despite no change in food intake, the high-intensity exercise group experienced significant decreases in both physical activity and core body temperature after exercise, leading to weight gain. Notably, they also showed relatively low blood corticosterone levels during waking hours.

Corticosterone, a stress hormone, follows a circadian rhythm, with levels low at bedtime and peaking upon waking, regulating physical and mental activity levels. Therefore, elevated corticosterone levels during wakefulness indicate a disruption in the corticosterone circadian rhythm. This can lead to decreased activity after exercise, which can lead to weight gain.

“Our findings suggest that a single session of high-intensity exercise can disrupt the circadian rhythm of corticosterone, reducing physical activity, body temperature, and weight gain,” the researchers wrote. “When designing an exercise regimen for effective weight loss, it is important to consider not only the calories burned during exercise, but also subsequent activity levels and circadian rhythms.”

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It's hard to lose weight through exercise alone.

They say it's possible only if you also follow a diet.

They say that keeping a diet diary is also very effective.